(1) Field of the Invention
This invention relates to a process for producing polyurea resin, and more particularly to a process for producing polyurea resin high in hardness, and strength, and excellent in heat resistance so as to be useful for a roller for making paper, steel, business machines, and the like.
(2) Description of the Prior Art
For the production of polyurea resin has been conventionally known a process for producing a polyurea elastomer which is adapted to react a specific oligomer amino benzoate compound obtained by reacting aminobenzoate with polyol, acting as a curing agent, with polyisocyanate, as disclosed in Japanese Patent Publication No. 32641/1985, Japanese Patent Application Laid-Open No. 135514/1981, and U.S. Pat. No. 4,328,322. Also, a process for producing a polyurethane urea polymer is proposed which is adapted to subject a compound obtained by adding a hydroxyl group to amino benzoate at a predetermined ratio, which serves as a curing agent, and polyisocyanate to a polyaddition reaction, as disclosed in Japanese Patent Application Laid-Open No. 89322/1984.
The former process for producing a polyurea elastomer using an oligomer amino benzoate compound is disadvantageous in that the so-obtained elastomer has a maximum Shore hardness as low as 45. When the molecular weight of a polyol moiety in the oligomer amino benzoate compound is decreased to avoid this problem, the viscosity of the mixture of the elastomer components increases to a degree sufficient to deteriorate the workability of the mixture, and the temperature dependence of the elastomer increases as well. Thus, the process failed to produce a polyurea elastomer of sufficient hardness and heat resistance.
A polyurethane urea polymer obtained according to the above-described latter process which uses an amino benzoate compound containing a hydroxyl group is clearly different in structure from a polyurea polymer. Unfortunately it had the disadvantage of decreased heat resistance due to its hydroxyl group of 10% or more at its terminal. The polymer also failed to exhibit a hardness of 70-80 in Hs(D) sufficient for use for a roll for making paper or steel. Its maximum hardness, in fact, was as low as 50 in Hs(D).